• Pediatric Infection and Vaccine
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• v.16 no.2
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• pp.183-190
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• 2009

Purpose : To evaluate the number and severity of adverse reactions after Japanese Encephalitis (JE) vaccination in children using different vaccines (inactivated vaccine or live attenuated vaccine) and to determine the ability and safety of the vaccines to provide effective immunization for JE. Methods : From August 2006 to February 2007, we conducted a prospective cohort study of the adverse reactions associated with JE immunization in Korea. We investigated common adverse reactions during the 4 days following immunization using telephone collaborations with four public health centers and nine pediatric clinics. Results : The mean age of children receiving the inactivated vaccines and live attenuated vaccines, respectively, were 1.4 y (range: 1 to 8.5) and 1.7 y (range: 1 to 8.3). The number of children that received the inactivated vaccines was 425 (64.6%). A total of 233 (35.4%) received the live attenuated vaccines. Fourteen children (3.3%) had more than one localized adverse event with the inactivated vaccine, and six (2.6%) had more than one event with the live attenuated vaccine (P =0.607). Systemic adverse reactions occurred in 5.2% vs. 8.2%, respectively, of these groups (P =0.131). Fever was more common in the live attenuated vaccine group than in the inactivated vaccine group on the day of vaccination (P =0.026). Conclusions : The rate of adverse events in our study was even lower than that previously reported. No significant difference in outcomes between inactivated vaccine and live attenuated vaccine was found in JE-immunized children. Fever was more common in the live attenuated vaccine group than in the inactivated vaccine group on the day of vaccination.

• Pediatric Infection and Vaccine
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• v.16 no.2
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• pp.175-182
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• 2009

Purpose : A number of countries have experienced an increase in pertussis during the past decade. In particular, there has been an increase in the incidence rate among adolescents and adults. To learn more about the current epidemiology of pertussis, we studied the prevalence and clinical characteristics of pertussis in children in Cheonan, South Korea. Methods : We collected nasopharyngeal aspirates of 118 patients who were treated for respiratory symptoms at Dankook Univeristy Hospital between March 2008 and September 2009. We performed multiplex PCR for detection of Bordetella pertussis in those aspirates. Results : Of the 118 patients, 10 (8%) were positive by PCR for B. pertussis. Six episodes occurred during the period July to September 2009. Nine of the 10 patients were less than 3 months old. Seven of them had not received DTaP vaccine. The mean duration of coughing before diagnosis was 10.9${\pm}$5.2 days. Ten patients (100%) had paroxysmal cough and 8 (80%) had post-tussive vomiting. Only one patient had fever. One who had complications that include pneumonia, atelectasis and pneumomediastinum developed an absolute increase in leukocyte count (84,400/$mm^3$). There was a statistically significant relation between vaccine being received and development of complications (P =0.033). Conclusion : We suspect that there was an epidemic of pertussis between July and September 2009. Further investigation by a pediatric or nationwide surveillance system is needed to monitor the changing epidemiology for pertussis.

• Pediatric Infection and Vaccine
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• v.16 no.2
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• pp.150-161
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• 2009

Purpose : Staphylococcus aureus causes a variety of infections, ranging from benign skin infections to fatal invasive infections. Recently, methicillin-resistant S. aureus (MRSA) infections have emerged in patients who do not have established risk factors. This study was conducted to characterize S. aureus infections in children with an emphasis on communityassociated MRSA infections at a tertiary care pediatric facility during a 3-year period. Methods : Four hundred twenty-nine cases of S. aureus infections diagnosed at the Seoul National University Children's Hospital between January 2004 and December 2006 were retrospectively reviewed. The cases were classified as hospitalonset (HO) or community-onset (CO), healthcare-associated (HA), or community-associated (CA) infections. Results : Among the 206 cases <1 year of age, 72%, 7%, and 21% were HO-HA, CO-HA, and CA infections, respectively, as compared to 48%, 28%, and 24% among the 223 cases >1 year of age. The proportion of CO-HA infections among HA infections (8.6% vs. 37.1%, P<0.001) and the proportion of HA infections among the CO infections (24.5% vs. 54.3%, P <0.001) were greater in older children than in infants. Overall, 57% of the isolates were methicillin-resistant. Twenty-nine (30%) of 96 CA strains were MRSA, and the most common site of CA-MRSA infection was the skin and soft tissues (26 cases). Conclusion : The methicillin resistance rate of S. aureus from CA infections was high and CA-MRSA was most often associated with skin and soft tissue infections.

• Pediatric Infection and Vaccine
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• v.16 no.2
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• pp.131-141
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• 2009

Purpose : In February 2007, an outbreak of methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections occurred in two newborns in the neonatal unit of Sahmyook Seoul Hospital. We performed this study to investigate the characteristics of MRSA nasal carriage among neonatal unit staffs and the effective infection control measures. Methods : Nasal swab specimens were obtained from the neonatal unit staff for the presence of MRSA. MRSA-colonized staffs were offered decolonization therapy with oral trimethoprim-sulfamethoxazole or 2% mupirocin ointment. Every 2-4months after decolonizaton, repeat nasal swab specimens were obtained. Also, samples from the neonatal unit environment and room air were collected. Results : Successful decolonization was achieved in 92% of the cases in 2 weeks after decolonization therapy, but most of the staffs were recolonized after several months. The nature of antibiotic susceptibility was changed from multi-drugsusceptible to multi-drug-resistant. The most frequently contaminated objects were dressing carts, computer keyboards, bassinets and washbowls. In environmental cultures using the settle microbe count method, the colony counts were decreased significantly at the last study period compared with the first study period in the neonatal room, breastfeeding room, service room, and dressing room (P <0.05). Conclusion : Effective control of sustained MRSA transmission within an institution may require prompt identification, treatment, and monitoring of colonized and/or infected staffs. However, nasal decolonization therapy may induce multi-drugresistant MRSA infection and had no effect on decreasing the MRSA nasal carriage rate in our study. Other factors might be more important, such as improving staff education, increasing hand hygiene practices, and environmental sterilization for controlling MRSA infections.

• Pediatric Infection and Vaccine
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• v.16 no.2
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• pp.123-130
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• 2009

Purpose : This study was performed to determine the clinical and epidemiologic characteristics of nosocomial rotavirus gastroenteritis. Methods : We retrospectively analyzed 628 medical records of patients with rotavirus gastroenteritis between 2001 and 2005. The patients were divided into two groups (the community-acquired group [528 cases] and the nosocomial group [100 cases]. The epidemiologic and clinical indices between the groups were analysed. For clinical comparison, 100 agematched cases were selected from the community-acquired group. Results : The male-to-female ratio was similar (1.4:1 vs. 1.5:1), but the mean age was lower in the nosocomial group compared to the community-acquired group (21.9${\pm}$15.5 months vs. 16.6${\pm}$10.3 months, P <0.001). The patterns of age distribution, annual frequency, and seasonal distribution were similar in both groups. The proportions of nosocomial cases in each year ranged from 9.8% to 22.4% of annual rotaviral infections, and these were not proportional to annual cases. The duration of fever appeared more prominent in the nosocomial group, and the severity of diarrhea was not different between the groups. The cases with a BUN >20 mg/dL were more in the community-acquired group (16% vs. 4%, P=0.01). Conclusion : The clinical and epidemiologic charateristics of nosocomial rotavirus gastroenteritis were similar and correlated to those of the community-acquired gastroenteritis.

• Pediatric Infection and Vaccine
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• v.24 no.3
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• pp.168-177
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• 2017

Purpose: The purpose of this study was to analyze the clinical features and risk factors of invasive infections caused by Lactobacillus spp. and Saccharomyces spp., components of commercially available probiotics. Methods: We analyzed demographic and clinical data from children ${\leq}18$ years of age with an invasive infection caused by Lactobacillus spp. or Saccharomyces spp. at the Asan Medical Center Children's Hospital from January 1998 to June 2016. Probiotic consumption data were also analyzed. Results: During the study period, a total of 24 episodes of invasive infections were caused by Lactobacillus spp. (n=16) and Saccharomyces cerevisiae (n=8). Along with the increase of probiotic use (755,594 [days/1,000 patient-admission days] in 2001 to 2005, 1,444,066 in 2006 to 2010, and 6,904,736 in 2011 to 2016), the incidence of probiotic-associated invasive infection increased ($R^2=0.70$). The median age of the patients was 1.8 years (range, 2 months to 17 years), and most of them had underlying medical conditions. The 30-day mortality rate was 20.8% (5/24), and 11 (45.8%) of these patients resulted from a severe invasive infection. We determined the risk factors for invasive infection to be: previous intensive care unit stay (odds ratio [OR], 3.0; 95% confidence interval [CI], 1.5 to 6.1] and the presence of a central venous catheter (OR, 2.2; 95% CI, 1.2 to 4.3). Conclusions: Although the probiotic-associated invasive infections rarely occurred in children, the incidence has increased along with probiotic pressure. Judicious use of probiotics is mandatory, especially in young children with underlying medical conditions and continuous surveillance will be needed to minimize the safety concerns.

• Pediatric Infection and Vaccine
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• v.24 no.3
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• pp.125-133
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• 2017

Purpose: After the introduction of Haemophilus influenzae type b (Hib) vaccine in 1995 in Korea, it was included in the national immunization program in 2013. In the post-Hib vaccine era, some studies in other countries reported that invasive Hib disease affects adults, especially the elderly and immunocompromised persons, more often than it affects children. To evaluate disease susceptibility, quantitative and qualitative analysis of anti-polyribosylribitol phosphate (PRP) antibodies were carried out in Korean adults aged 20 to 85 years. Methods: Sera were collected from 39 healthy adults (20 to 50 years of age) and from 30 elderly adults (75 to 85 years of age) who did not have immune-compromising conditions. The concentration of anti-PRP immunoglobulin G (IgG) and serum bactericidal indices (SBIs) were measured by enzyme-linked immunosorbent assay and serum bactericidal assay. Results: Geometric mean concentrations of anti-PRP IgG and geometric mean SBIs were $0.88{\mu}g/mL$ (95% confidence interval [CI], 0.17 to 3.85) and 354 (95% CI, 50 to 2,499) in young adults and $1.67{\mu}g/mL$ (95% CI, 0.53 to 5.24) and 449 (95% CI, 146 to 1,376) in elderly adults, respectively. When the threshold of seropositivity for anti-PRP IgG was applied as 0.15 or $1.0{\mu}g/mL$, which is the protective antibody level in children, seropositive rates were 87.2% or 53.8% in young adults and 100% or 60% in elderly adults. The seropositivity rates of the SBI ($SBI{\geq}4$) were 82.1% and 100% in the groups, respectively. Conclusions: Most subjects in the adult and elderly adult groups display immunity to Hib based on quantitative and qualitative antibody levels, but not all. Because high immunization and low Hib circulation rates may reduce the natural Hib immunity in the population, monitoring Hib immunity as well as disease are needed continuously.

• Pediatric Infection and Vaccine
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• v.24 no.3
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• pp.134-140
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• 2017

Purpose: Severe combined immunodeficiency (SCID) is the most serious form of primary immunodeficiency. Infants with SCID are susceptible to life-threatening infections. To establish newborn screening for SCID in Korea, we performed a screening test for T-cell receptor excision circle (TREC) and ${\kappa}$-deleting recombination excision circle (KREC) in neonates and investigated the awareness of SCID among their parents. Methods: Collections of dried blood spots from neonates and parent surveys were performed at the Samsung Medical Center and Cheil General Hospital & Women's Healthcare Center in Korea. The amplification crossing point (Cp) value <37.0 was defined as TREC/KRECpositive based on cutoff values from measuring multiplex real-time polymerase chain reaction. A Cp value >39.0 was defined as negative. Results: For TREC/KREC screening, 141 neonates were enrolled; 63 (44.7%) were male. One hundred forty neonates (99.3%) had positive TREC/KREC results at the time of the initial test; 82.3% and 75.9% were positive and 17.0% and 23.4% were weakly positive for TREC and KREC, respectively. In one neonate (0.7%), the initial TREC/KREC test result was negative. However, repeated tests obtained and confirmed a positive result. For an awareness survey, 168 parents were engaged. Only 2% of parents (3/168) knew that the newborn screening test for SCID had been introduced and performed in other countries. Eighty-four percent of parents (141/168) replied that nationwide newborn SCID screening should be performed in Korean newborns. Conclusions: In this study, newborn SCID screening was performed along with assessment of public awareness of the SCID test in Korea. The study results showed that newborn SCID screening can be readily applied for clinical use at a relatively low cost in Korea.

• Pediatric Infection and Vaccine
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• v.25 no.2
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• pp.72-81
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• 2018

Purpose: This prospective study aimed to investigate the therapeutic efficacy of lamivudine in children with chronic hepatitis B virus (HBV) infection. Methods: During July 2003 through October 2015, children with chronic hepatitis B who visited our institution were included in this study. Fifty-five patients, who received first-line treatment of lamivudine (3 mg/kg, 100 mg maximum) for over three months, were enrolled. After initiating lamivudine, alanine aminotransferase (ALT), HBV-DNA, and HBV markers were followed up at 1 month, 3 months, and every 3 months, thereafter. The treatment endpoint was determined as 1) normalization of ALT, 2) HBeAg seroconversion, and 3) anti-HBe positivity for twelve consecutive months. Results: Thirty-one male (56.4%) and 24 female (43.6%) patients were included. The mean age at treatment initiation was 8.1 years. The mean duration of treatment was 23.4 months. ALT normalization was found in 98.2% (54 of 55). Anti-HBe seroconversion was found in 70.6% (36/51). Loss of HBsAg was found in 10.9% (6/55). All biochemical responses occurred under age seven. The rate of virologic response (defined as HBV-DNA <2,000 IU/mL) at six months after treatment initiation was 78.7% (37/47). At twelve months after reaching treatment endpoint, 87.2% (34/39) maintained their virologic response. Resistance to lamivudine was found in 16.4% (9/55). Conclusions: Lamivudine treatment in Korean pediatric patients with chronic hepatitis B showed better outcomes compared with other studies that implemented similar protocols in foreign populations. Further studies are needed to investigate the efficacy of newly recommended antiviral drugs on the Korean pediatric population.

• Korean Journal of Microbiology
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• v.40 no.4
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• pp.295-301
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• 2004

Recently, the rapid increase and global spread of extended-spectrum $\beta-lactamase$ producing clinical isolates has become a serious problem. The incidence of extended-spectrum $\beta-lactamase$ producing clinical isolates of Escherichia coli in Korea and susceptibility to antimicrobial agents were investigated. Total 233 isolates of E. coli were obtained from urine from hospitalized patients in Guro hospital, Korea University in 2001. One hun­dred and eighty four isolates $(78.9\%)$ were resistant to ampicillin, 80 isolates $(34.3\%)$ were resistant to ceph­alothin, 93 isolates $(39.9\%)$ were resistant to gentamicin, and 64 isolates $(27.5\%)$ were resistant to norfloxacin. Among 233 isolates, 17 isolates $(7.3\%)$ were positive as determined by the double disk synergy test. When min­imal inhibitory concentrations were assayed with additional 6 antimicrobial agents, 13 isolates $(76.5\%)$ were multi-drug resistant to at least four different class antimicrobial agents. Extended-spectrum $\beta-lactamase$ were characterized with isoelectric focusing gel electrophoresis and DNA sequencing. They were TEM-1 in 5 iso­lates, TEM-15 in 1 isolate, TEM-20 in 1 isolate, TEM-52 in 4 isolates, TEM-1 and AmpC in 2 isolates, TEM-1 and OXA-30 in 1 isolate, TEM-1 and OXA-33 in 1 isolate, TEM-1, CTX-M-3, and AmpC in 1 isolate, but SHV was not detected. Antimicrobial resistance genes were transferred to animal isolate of E. coli (CCARM No. 1203) by the filter mating method. Extended spectrum $\beta-lactamase$ producers studied in the current study have low correlation to each other as determined by random amplified polymorphic DNA and pulsed field gel elec­trophoresis. This is a contradictory result from the general hypothesis that extended-spectrum $\beta-lactamase$ pro­ducers in one hospital is a result from a clonal spread.